(From The LOWDOWN, June, 1997.) "The LF Notebook" The Mailbag, News and Comments About LF Radio, Etc. John H. Davis, Box 367, Warm Springs, GA 31830 - E-mail - longwave@mindspring.com - Web - http://members.aol.com/lwcanews/ [ TWO PICTURES ACCOMPANY THIS ARTICLE: ] http://frodo.bruderhof.com/longwave/notebook/n51pic1.gif http://frodo.bruderhof.com/longwave/notebook/n51pic2.gif "Now for something completely different." Monty Python must have had this past month in mind. Almost everything turned out to be completely different from what I expected. The expected travel plans fell through (I was grateful for the chance to catch up on sleep instead, though); the Longwave/Part 15 BBS ended; it looked for a while as if we would have the usual complement of columns instead of the beacon lists being AWOL; then we end up with a mostly-features Notebook after all. As for this last week before deadline...well, you wouldn't believe it if I told you. I'm not sure I believe it, and I'm positive I don't understand most of it. And you've heard the saying about a first time for everything; well, this morning, during final assembly of this column, with only two hours before the Post Office closes, Microsoft Publisher crashed on me for the first time ever. Talk about panic attacks! Well, let's just plunge on in and see what we can do. I think you'll find the column interesting. It certainly is different. Ch-ch-ch-changes... As I mentioned above, the Longwave BBS is no more. Shortly after last month's column was in the mail to headquarters, I began monthly maintenance on the BBS. With usage figures from our new Longwave Home Page counter in mind, it suddenly struck me...the BBS and its phone line are costing as much as the Internet activities, but reaching well under one percent of the number of people. It was abruptly and painfully evident that the time had come to say farewell, so I posted messages to that effect, and it shut down on May 6 (coinciding with our most recent telephone cable failure in the neighborhood). It has become more practical and far less expensive for most people to use the Internet for messages and file access, so I hope this move will let us serve the needs of members and prospective members better. There were over 1500 "hits" on the Longwave Home Page in April, and the Message Board area receives over 350 hits a month! People reached us from high-use areas such as Canada, Japan, Sweden, to the Russian Federation, South Africa...even the Faroe Islands. Most gratifying. Tim Brannon (KF5CQ) nicely summed up my own feelings about the BBS: "It served its purpose admirably, but technology marches on, in keeping with other developments in the hobby today." Consol-ation Prize On the Longwave Message Board this past month, Jacques d'Avignon posted this inquiry: "There is still a LF Consol station in Stavanger, Norway. I understand that it will close soon and I am trying to get a recording of it from some friends overseas. Does anyone have the frequency of this station?" Pierre Thomson "did a bit of snooping in the aero charts," as he put it, and found the station listed on 319 KHz, with ID LEC. Consol didn't ring a bell with your columnist, but fortunately Jacques provided this additional fascinating information: "The CONSOL station left in Stavanger is the last one left from a group of 3 that were operating in Europe. One station was at Bush Mills in the UK and the other was in Ploenis in Spain." "To get direction from this station you need a special chart and you count the number of dots and dashes between the ID signals. Then by looking at the chart you get one azimuth. So if you have 3 stations, you get a good fix. The CONSOL range is 1000 nautical miles." "For 'older' people, TUK on 194 was originally set up as a CONSOLAN... long range CONSOL station. There was another one on the West coast, I believe that it was LAX on 196." "There is very little left in the literature on this. Even older listeners in Europe are not aware of it, though the station is still on the air." Who, What, Where, and GWEN That bane of LowFER existence, the Groundwave Emergency Network, is apparently being phased out. Ironically, just as there has been renewed interest in GWEN operation from our members, reports started circulating that the military now consider satellite communication more reliable under the very circumstances for which GWEN was created. The first inkling I had of this was a letter from Rick Wright, which appears in the Mailbag section. Shortly thereafter, Pierre Thomson (KA2QPG) wrote with this quote from the May, 1997, issue of QST, on page 46: "The introduction of Milstar will also permit the retirement of older and less capable systems such as the Ground Wave Emergency Network." Pierre notes, "This was written by Charles Keene of the US Strategic Command. He ought to know what he's talking about. So let's hope we will soon have the full 160-190 KHz band for Lowfer activity!" (I'm especially grateful to Pierre for passing this along, as my own copy of the May QST is off in postal limbo somewhere.) Intriguing, eh? Fortunately, another piece of the puzzle appeared in the form of a brief request from Walt Fowler (KC5ZDX; wfowler@jumpnet.com), for reception reports on a new Differential GPS station: "The GWEN station at Appleton WA has been converted to 300KHz and is transmitting DGPS corrections. The station is delivering 500W ERP at 300KHz. How far can it be received??" Of course, your inquisitive columnist had to know more. Could this really be so? How did Walt find out something like this? Well, it turns out he has first-hand knowledge in the matter! I'll let him explain it in his own words: "I work at Starlink Inc. We installed a 1KW transmitter and coupler that we designed for DGPS transmissions. The transmitter went on the air last week (mid-May) with an incredible efficiency of 50 percent. The high efficiency is due to the antenna being 300 feet tall with 12 each 200- foot top load radials. The next best efficiency DGPS beacon was at Sallisaw OK with 25 percent. "Our DGPS beacon receivers decode the MSK modulation which includes a transmitter identification number as well as Latitude and Longitude of the Transmitter. The receivers are quite expensive because of the DSP required to demodulate the MSK modulation however the guy that does DSP programs on a PC with multimedia analog input could write a program that would decode the data with a receiver that converted the signal into the audio band. The bit rates for DGPS beacons in the USA are 100 and 200 baud (100 for the Appleton beacon). I design receivers and transmitters but computer programming is not a strong point with me. "There is a plan to turn all the GWEN sites over to the Coast Guard or some federal agency we think by the end of 1998, depending on how the testing goes on this site. Appleton was put on the air for at least a year for a Federal Railroad test designed to improve railroad safety and allow more trains on the same track by using exact position information provided by DGPS. "Starlink has a web page at http://www.starlinkdgps.com. Information about DGPS beacons across the world can be found there. "The plan to cover the USA with DGPS was announced at a European conference by the assistant secretary of DOT. GWEN conversion should be a feather in the politicians cap for converting a cold war system to civil use. The cost savings are tremendous when you consider 22 sites which will cover almost the whole USA in daytime conditions, with antennas and buildings already in place. The minimum field strength the Coast Guard considers adequate is 75 Microvolts/meter; these are fairly strong signals but are required to receive digital data in thunderstorms. "MSK modulation is the most efficient form of modulation when you consider bit rate verses bandwidth, for example for 200 baud data only 200 Hz of bandwidth is required. MSK can be looked at as FM or FSK, a digital 1 is defined as an advance in carrier frequency of 1/4 the baud rate. Example for 200 baud shift frequency... up for 5 milliseconds by 50 Hz; this will appear on the carrier as an advance of 90 degrees in the bit time of 5 ms. A zero is a shift down by the same amount. The data bits are synchronized with the carrier frequency so the bit rate must be a sub-harmonic of the carrier frequency. "A simple way to demodulate MSK is to use a narrow band discriminator just like an FM receiver. The output of the FM detector will be the data bits. This detection method will suffer at least 3dB and more like 5dB of sensitivity loss when compared to a phase lock loop, but is a way to decode the data with out DSP. "I will find the documentation on data formats and see if I can get it posted, I don't know how to do this but it will be a learning experience." I certainly thank Walt for his efforts and generosity in making all this information available. A block diagram of Differential GPS correction at work is in n51pic1.gif, adapted loosely from the Starlink Web site. It's based on the idea that, whatever the dithering may be on the GPS system, a receiver at any accurately known location can be used to derive the error between the GPS reported position, and the known true position. A correction signal can then be encoded that will allow other receivers to achieve high accuracy too...perhaps as close as one meter for the most expensive GPS/DGPS receiving combinations! You might expect a DGPS transmitter to look like something out of Star Trek, but it doesn't necessarily. Starlink's TX-1000 transmitter (n51pic2.gif) is a basic, solid-looking industrial unit. Using Class D RF amplification, it does have impressive efficiency figures, of course. It can work from the AC mains, or from a 96 V DC backup supply. Power levels are 250, 500 or 1000 Watts. The extent of DGPS coverage can be found in several charts for individual regions now on the Coast Guard Web page. (You can find their site through the LF Utilities section of the Longwave Home Page.) With the kind of efficiency likely to be had from the GWEN antennas, operating them in the 282 to 326 kHz range, nationwide coverage appears to be a reasonable goal. The system is still in interim operational capacity, but is hoped to reach full operation in 1998. The Lowdown on Loran Yes, it's true what David Jones passed along from the Naval Observatory last time. Loran C is slated for termination in the year 2000. This is one of the results of the new Federal Radionavigation Policy. The entire document is now available on the Coast Guard's Web site. The document is four megabytes long -- in compressed form! Whither WWVB? Fortunately, this is one old LF friend that's still around. You may recall mention of a power upgrade for WWVB a few months ago. We now have the whys and wherefores of this, and will bring you the information in July. The station should be ready to triple its power in September, if all continues to go well. Top End Tidbits The Top End column is likely to return in regular form next month, but I wanted to briefly mention two items and pass along one question. The first news item involves a station on 1630 kHz, identifying itself as WDKW ("The Klaw"), Dundalk High School, somewhere in Maryland. I say somewhere, because Hank Holbrook (407 Arundel Road, Dunkirk, MD) received one address for them when he called the phone number given on the air... and the same street address, but a different city and Zip on the envelope bearing his prepared QSL and a letter from the operator, Thomas Pless. He also observes that the envelope had a hand-written return address. The station is said to use a Radio Systems TR-20 transmitter and a Morad SF-530SP 25-foot antenna. This configuration would be typical of a TIS installation. However, Mr. Pless claims the station operates under Part 15, and "falls under the new rules pertaining to 'free radiators'..." Hmm. Where have we heard the term "free radiators," or its first cousin, "free broadcasters," used before? Hank's reception was on April 24 at 9:05 AM. The address is 1901 Delvale Avenue, in either Dundalk, MD 21222, or Baltimore, MD 21228 ("So take your pick -- HI!" Hank notes.) Might want to listen for this one soon, before the FCC discovers it has some "new rules" it didn't known about before. The other news item comes via Robert Kramer's medium wave DX page on the Web, and deals with a creative use of Part 15, albeit one that appears more likely to fall within the Part 15 rules as most of us know them: "Charles Bernth reports that there is a new low power broadcaster operating out of Bridgeport, CT on 1630 kHz. The station operates with 100 milliwatts using the ID WSPN. Programming consists of jazz, reggae & Spanish. The station has 6 translators located throughout the city. The station address is: Box 9412, Bridgeport, CT 06601." Check out Robert's Web site at: http://users.aol.com/RKDX -Mike Hardester (e-mail: 2Lakota@Coastalnet.Com) checked in with this inquiry, in hopes someone may be able to shed some light: "Still no DXing here, but I did receive an inquiry from another DXer (Larry Godwin in Montana). Larry copies code, and needs help IDing the following: >>From Larry Godwin, Missoula, Montana (lbg@selway.umt.edu) >>I heard an unidentified beacon on approx. 1685 kHz. on April 21, 1997, >>around 1200 GMT. It transmitted dual Morse-code messages. In >>low-pitch code were the letters "IRA" or IRI." In high-pitch code I heard >>what seemed "CRT" or "RRT" and also "NR." The time of reception suggests >>the Pacific area. I don't see anything similar listed." "I couldn't find anything in my references, and since the R-70 isn't working, no can check nothing from here. Ideas?" On To The Mailbag -Stephen P. McGreevy has made some neat enhancements to his Web page in recent months (http://www.triax.com/vlfradio/index.htm). Be sure to check it out! -Lyle Koehler (LEK, MIN, K0LR; Aitkin, MN; k0lr@emily.net) writes, "This will be a very short report because we're going into the summer slump in LowFER/MedFER activity. Beacon OK was still readable here until lightning took out Bill's transmitter at the beginning of May. I'm still hearing local beacons SAM and I." "Regarding BPSK activity on the ham bands, the only news to report is a successful 6-meter BPSK QSO with Clair, K0CJ, who lives about 115 miles south of me. Clair's rig had an intermittent modulation problem that would cause the output to drop from 50 watts down to a level that hardly showed up on his wattmeter, but his BPSK signal kept printing. We may run a more controlled test when his radio comes back from the repair shop." "Murphy's Law dictated that of the two articles I submitted to The LOWDOWN last month, the one with the error in the schematic got published first. If you can, please make sure the corrected schematic for the BPSK/CCW dual-mode identifier makes it into the June LOWDOWN." -Bob Hoffswell (BOB, AA9DH; Mahomet, IL) has decided to leave BOB on the air through the summer. "I made a test with and without the radial wires on the antenna system, leaving only a ground-screen composed of five pieces of 2' by 30' chicken wire laid on the grass. My test with the full system gave a pretty good, 569 signal at about 60 mi using my portable rx. A few weeks later, the signal at about the same place was nil. A few weeks after that at a Hamfest 90 mi from here, the signal was weak, but pretty good copy, despite the fact that I was near Chicago and a lot of AM stations. So, what can I say! As time permits, I'll upgrade BOB for next season and fool around with movable/mowable grounds, and I'd be pleased to hear from anybody that hears BOB. I still remember that BA was great here last August before he added his winter ground system, and even with the extended grounds last winter, BA was not much better here, and was often pretty weak or uncopyable. Go figure, as they say!" "Despite it all, and few reports, I still enjoy LF work. It's a real QRP endeavor. Mostly, I'm the only one listening to BOB, but it still is a joy to hear it as DX!" -Darwin Long IV (DJL) sends a summer beacon update for DJL: "As of today, May 9, I have begun operating my beacon from a new location, about five miles southwest of the former location. The transmitter is now in Newbury Park, CA, still grid location DM04. A much-improved antenna and ground system is now being used (30' T-antenna with four-wire 8'x20' top-hat)." -John R. (Rick) Wright (R, KA5YWH; Durant, OK) reports, "I have recently heard through Dr. James Britton (electronics department here at SEOSU) that the GWEN system may be converted to a precision GPS beacon network intended for FAA use, I presume for airport precision instrument approaches....Have you heard of any such changes in GWEN's use?" "GPS is really interesting stuff....I know that many of us LowFER experimenters would like to see GWEN go out of the picture entirely; however, in a really bad national emergency, GWEN is essential (that is my honest view, no doubt colored by my prior experience as a USAF electronic warfare officer, one who worked in the original C3I system - NORAD). Notwithstanding the apparent end to the Cold War, we are not out of the woods, and some of these disarmament developments show more enduring faith than I've seen from my Baptist friends! (I was raised Baptist.)" "Incidentally, James is trying to build a LowFER beacon. I'm encouraging him." "Sunday afternoon, May 4, 1997, I went out to the "quiet site" about 2 miles SW of my home (out in the prairie and away from power lines) and searched for the TEXAS beacon using a regenerative preamp fed by a 12 ft whip antenna. I still use the little Sony ICF 2002 receiver. I found TEXAS on the published frequency, a strong signal of communications quality at my distance. TEXAS transmits its ID twice, then goes key-down for several seconds, after which the process repeats, etc. Does he have BPSK in the key-down part? I also searched for but did not find OK. There was some static today, and Davenport is further away." "I'm also hearing that LORAN-C's days are limited, which is really hacking off a bunch of pilots. Quite a bit of money is invested in those instrument panels." -Robert Laney (RL; e-mail: RLLaney@aol.com) checks in to say "I will try to have RL on this summer, but it will be intermittent because of the usual shut downs for T-storms and the threat there of. We have had more threats so far than actual storms. Seems like spring will never get here." "The index--I have not forgotten about it. In fact, I tried the other night to get a good ASCII file for 1995 from the Lotus file, but I'm having problems with cut off columns in the transition. But, I think that it can be done. Wish I knew more about Lotus 5, but I am learning. I am going to add 1996 to the master file and slowly work my way back in the years." -Kevin Carey (kcarey@mdsroc.com), longwave editor of Monitoring Times, wrote with kind words for the Web page and this column. "It makes me feel like I'm sitting around a big table of hobbyists asking each one 'what's new?'" I think Kevin has hit upon exactly the feeling we try for with this column, and of course, I owe that all to you, our members and readers. It's your news and comments that make it work. Footnotes. Enjoy your summer, and let us hear from you soon. 73. - - -